ON ATM08PHEBIC WAVES. 
359 
The abrupt and precipitous rise that occurred at all the northern stations 
and especially at Galway, appeared to be compounded of the anterior slopes 
of the two waves that succeeded ; first, the wave-crest that passed over the 
area from the south-west on the 4th; and second, the posterior slope that 
produced the diminution of pressure from llic south-east towards the north¬ 
west at the same time. About noon of the 6tli the baromet«'r began to rise 
rapidly at Limerick and Helstone? it was nearly 9 at night when the rise 
commenced at Jersey and London. It also conxniouccd about the same time 
at Largs and Stornoway; at a later period at Rami^ate, and about midnight 
at Arbroath and the Orkney*. The anterior slope of the second south¬ 
westerly wave was fully established over the area by midnight of the 6th, 
The intersections of the Limerick, Helstone, and Jersey curves dearly indi¬ 
cate the presence of the anterior slope of Urn second north-westerly wave. 
An intersection of tiic Ranisgate anil London curves, from the transit of 
the trough succeeding the posterior slope of the north-west wave 
occur. From the rise of the 6tb to nearly the end of their course they run 
together; the curves at Helstone and Jersey run nearly together from the 6th 
until the 11 th, ami this would indicate that the trough oither remained in the 
neighbourhood of Jersey, or that it was very broad and nearly of the same 
level. Limerick is usually *10 above Helstone, so that wc have a diminution 
of pressure from Limerick to HeLtone of that amount. The observations 
from Hobbs’ Point agree with this diminution, and clearly indicate the pre¬ 
sence of the anterior slope of tlie succeeding north-west wave, fkis wave 
does not appear to have extended much further towanls the north-east than 
the line joining Ramsgate and Limerick, as the original slope from south-east 
to north-west exists for sevtual days after, although much contracted, unless 
the south-westerly slope produced the appearance of a succeeding wave. 
The abrupt rise which commenced on the Gth terminated about 9 a.m. of 
the 8th, when the barometer passed a slight maximum at Limerick: this 
maximum aUo occurred in a slighter degree at Helstone; at Galway it was 
very decided, and can be traced more or less in all Uic northern curves. 
This rise was greatest at the north-western stations, those that ware situ¬ 
ated tow.arcis the trough of the first north-west wave: it appears to have been 
occasioned by tlic anterior slope of a south-west wave succeeding the south¬ 
west wave that transited on the 4111; by its influence the curves at Stornoway 
and Largs were brought to a level with the London and Ramsgate curves, 
and this would inilioate the direction of the crest. A careful consideration 
of tho curves leads to the conclusion that the two south-west waves were en¬ 
tirely independent of each other, the greatest swell of the first occurring in 
the neighbourhooil of Jersey, that of the second in the north-west; their 
directions also appeal- to l»e decidedly diflerent. 
Pluenomeiui of tJw JiaTowetric Rha oltsei've^ wer the area on the Gth, lih, 8<A, 
9/A and KVA of November 1846. 
(1), (2). Helstone and Llineriek, Nov.6,9 A.M.— This rise was first observed 
at HcLstone and Limerick, and at these stations evidently resulted from the 
anterior slope of the wave, or rather waves, that succeeded those that transited 
on the 4th and 5tli. The rise at HeUtone was at first rapid, but at 9 a.m. 
of the 7th it received a slight check. A very decided bulge occurred during 
the night h<>tween Uie 7th and Sth ; at 9 a.m. of the Hth the barometer passed 
a slight maximum, the principal maximum occurring at 9 p.m. of the 9th. 
At Limerick the rise was much more rapid; from the intersection of the 
curves at midnight of the 6th, it appears certain that the anterior trough of 
the north-west wave had passed Helstone; the rapid rise, probably from the 
